Improvement in differential gear-power machine



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Letters Patent No. 75,304, dated .March 10, 1868.

IMPROVEMENT IN DIFFERENTIAL GEARTPOWER MACHINE.

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TO ALL WHOM IT MAY CON CERN:

Be it known that I, .HENRY FRANKLIN SHAW, of West Roxbury, in the county of Norfolk', in the State of Massachusetts, have-invented a new and improved Differential Gear-Power Machine; and I do hereby declare that the followingl is a full and exact description thereof, reference being had to the accompanying drawings and to the letters of reference marked thereon. I

The nature of Vmy invention consists in greatly simplifying and improving that class of power-multiplying machines known as differential gear. It is well known to mechanics that if a cylinder, having spur-gear cut upon its external surface, be made to roll upon spur-gear cut upon the internal surface of a second cylinder,

' the relative, rotatery motionof the two cylinders will depend upon the difference of the relative diameters of the two pitch lines. Thus', if the two'pitch lines are identical, the two will have no relative rotatory motion; if they revolve atfall, they must both revolve with the same velocity. If we make the pitch line of one smallerthan that of the other, and give one of the gears a motion around a central point, but still so confining it as-ul-ot to admit of a rotatory motion on its own axis, it will be found that the other gear will be forced to revolve witha yelocity that holds the same relation to the velocity with which the actuating gear moves, as a mass, around its central motion, that the difference between the diameters of the pitch lines bears to the diameter of the larger pitch line.

An invention made by me, and described in patent dated May 21, 186?, and numbered 64 "P15, works upon the principle above set forth. By my present'inventien, I hang both these gears ecccntrically. upon a shaft, which is free to revolve'indepcndently of either gear. The gears themselves are also free to revolve around their own axis, but are hung eccentrically upon the free revolving shaft. Now, if one of these gears is held, and the shaft he made to revolve, it will be found that the unconfined gear will have a slow motion around its own centre. Again, if the motion of both of these gears is resisted by'an equal force, it will be found that they will revolve slowly in opposite directions. I take advantage of this principle, by attaching two ropes to the weight to be lifted or resistance to he overcome, and connecting these ropes, one to a pulley connected with onegear, and the other to a pulley connected with the other gear, so that when the central shaft is made to revolve,the pulleys act mutually as buttresses for cach other, and thus overcome any resistance'oiercd to their tendencyto relative motion. As both pulleys are free upon the actuatingshaft, and as the two r'opes draw upon opposite sides, a perfect equilibrium of tensionupon each rope is maintained. In the drawings--y y Figure lfreprescnts' a perspective view of my invention when rsed asia. hoisting-gear of an elevator.

Figure 2 represents a combined pulley and internal gearin lplan and section. i

Figure 3 represents a combined pulley and external gear.

Figui-e4 is a section through both gears.

Figure 5 represents'the actuating-shaft. v t

L L, iig. l, represent the two standards or supportinghpost's of an elevator, in which is hung'theactuating'- .shaft U, shown enlarged in 5g. 5. E is a crank for turningthe actuating-shaft. M M, fig. 1, are hangers for the purpese'of giving additional support tothe shaft C. F P K, iig. 1, represent the platform and frame of the elevator-carriage. H is a cross-bar attached to the upper 'bar K of the frame of the carriage. v CZ d are two cords attached to the ends of the har H, and to the pulleys A B.

The pulleys A B arc made as represented in figs. 2 and 3, that is, the pulley A is provided with an extennal spur-gear, Q, iig-:3, while the pulley B is providedwith Tan internal spur-gear, Q, iig. 2. .When in4 use thse two gears and pulleys are placed together,'as shown in figs. 4 and 5, and hung on'the shaft C, the pulley A` ontthe eccentric, a, and the pulley B on the eccentric, b.

By a careful examination ofthe drawings and above description, it will be understood that ifthe shaft C` be revolved, and ifnn equal resistance he offered to the revolutionof the two pulleys, that is, such a resistance as would be offered by the two cordsA d d', iig. 1, a differential motion will take place between them, and in case the 'shaft is turned in the right direction, the weight will be raised, but if turned in the opposite direction, the, weight will belowcred. y l ,A

Since the cords d d pull from opposite sides of the shaft C, and the gears connected by the two pulleys always mesh together, there will be perfect equilibrium of strain upon the two cords, thatis, one will act exactly against the other, ,and there will 'he no tendency of the weight to r'un down; vhelma in my apparetusI require no pswls or brakes tohold the weight when partly raised.

The necessary relative eccentric motion can be obtained by a. single eccetic on the shaft C, but the machinedoes not look so well in operationi Having thus describedmy invention, I will lnow set forth my claim. A l

What I claim s my invention, and desire'to secnreby Letters Patent of the United States, is-

The two pulleys or winding-barrels in the di'erential gear-powet.machne, conneeted by gear as described, e'ccentrically hung upon a. free revolving actuating-shaft, operating substantially-as desoribed, and for the purpose set forth.4 i

HENRY F. SHAW.

Witnesses:

WILLIAM EDsoN, A. HUN' BERRY. 

